Sound dampening

Dynamat's web site states that thier products will increase the SPLs of car audio sound systems.  Does sound dampening really make a difference for soneone who doesn't compete?  If it does make a difference, are there other brands that are cheaper than Dynamat.  Dynamat has a trunk kit that is applealing, but their prices are not.  I have also seen on some web sites spray cans of sound dampening material.  I just want the most effective, easiest to install, and cheapest product.  But if the increase in SPLs or sound quality isn't very much then I won't even bother.  Any input would be appreciated.

yes damping material work very well. it stops or lessens metal resonance/vibrations.roofing/flooring supply shops sell similar material much cheaper than dynamat.Wal-Mart sells expanding spray-foam as well for sound damping over in the paint dep't. use this for areas where mat isn't feasible, like nooks and places you can't stick the mat.you want to lay 2" strips of mat, 6" apart at a 45deg. angle over all metal lsurfaces for ideal damping.-GlassWolf

Pioneer Stage-4, Orion, DynAudio, Fi